One substantial impediment to achieving high thermal efficiency in gas turbines resides in the inability of certain components, most notably the turbine wheel, turbine wheel vanes and turbine nozzle, to operate reliably and with long life at the high temperatures required to obtain high degrees of thermal efficiency. One means of overcoming the difficulty is to employ relatively exotic materials in the manufacture of these components, that is, use materials that are capable of withstanding the high temperatures as well as the thermal cycling associated with operation of the turbine. This solution, however, is an expensive one and is accordingly is not susceptible to use on a wide scale.
As an alternative, the art has preferred to seek improved schemes for cooling the components so that the same may be exposed to gases at ever increasing temperatures but without being heated to those temperatures themselves. Not infrequently, various means of distributing compressed air from the compressor of the engine to the components requiring cooling by means of various passages have been employed. All too frequently, however, the passages may be tortuous or large in number in relation to the vanes employed and otherwise unduly complicated. Such passages may be very small, particularly in small turbines and hence prone to plug. In addition such small passages are costly to make.
The present invention is directed to the provision of simple but highly effective cooling means for turbine nozzles in the form of low cost, large coolant carrying passageways, and obtains the added benefit of allowing the nozzle to be used for turbine wheel containment.